The present invention is directed toward a medical prosthesis and more particularly toward a medical prosthesis for alleviating or preventing epileptic seizures and other clinical conditions of the nervous system.
Certain diseases or malfunctions of the nervous system are associated with abnormal neural discharge patterns. Some of these are more or less continuous or chronic, such as is the case with Parkinsonism. Others may be discontinuous, characterized by threshold phenomena, such as in epilepsy. The time of onslaught of grand mal or petit mal seizures is often predictable by neural discharge monitoring or other means, even when the exact causal nature of the precipitating dysfunction is not understood.
It is recognized, however, and confirmed by experimentation, that the introduction of certain control signals of the proper configuration, intensity and duration can act as a means for discharging or modifying hyperactivity in the brain. The superposition of such corrective measures, whether by the generation of proper interference patterns overriding control pulses or cancelling signals, acts in a way to inhibit the normal progress of the seizure and may prevent it altogether. It is also possible that control signals of proper magnitudes when applied to associated neural tracts can cause neural activity to return to its normal state.
Corrective signals of this type can be generated by appropriate electrical pulses or waves applied to neurons. Neurons produce electrochemical signals called action potentials which can be triggered by electronic devices.
The primary intent of the present invention is the implanation of a neurocybernetic prosthesis in the human for epileptic control. The operation of the prosthesis is based on the principle of augmenting inhibitory processes in the brain to control states of hypersynchronous neural discharge.
Currently, approximately seventy-five percent of epileptics are responsive in some degree to drugs, although undesirable side effects may force discontinuance. Drug therapy necessitates a continual, general effect on brain cells and other tissues, not infrequently resulting in undesirable side-effects whereas epilepsy constitutes an interrupted condition occuring at an approximate average of two convulsions per week. Unlike drug therapy, a neurocybernetic prosthesis can be made operational just during the period of the convulsion by utilizing sensor feedback or manual control. Also, objective evaluation of drug effectiveness involves determination of chemical levels in the blood which is a very costly procedure. Since hyperactivity of the brain is the basis of many nervous system aliments such as Parkinson's disease, cerebral palsy, spasticity, motor disorders, etc., such a prosthesis would also be useful for these chronic nervous illnesses.
An attempt had been made in the past to provide a neurocybernetic prosthesis for alleviating epilepsy and other disorders. It did not, however, meet with much success for several reasons. This prior attempt included a device which had to be implanted into the brain (cerebellum) thereby requiring expensive and extremely risky brain surgery. Furthermore, the implanted device was found to produce tissue trauma in the cranium. It was found that there was a progressive deterioration of cell bodies in the cerebellar cortex due to the electrical current and excessive regeneration of connective tissue.